Gauge for steep faced threads



- Jan. l5, 1946. R. T. PENN GAGE FOR STEEP FACED THREADS Filed March 28,1944 2 sh'eets-sheet 1 Patented Jan. 15, 1946 UNITED `STATES PATENTYlOFFICE GAUGE' FOR STEEP FACED' THREADS' Raymond-1L T. Fenn,Springfield; V-t., assignor to Bryant Chucking. Grinder Company,Springfield, Vt., a.- corporation of Vermont Application MarchrZS,19445, Serial No. 528,399

(Cl. 33e-199) 3. Glaims.

When. gauging. threads, gaugingI anvils which mate the, threads to begauged are. employed. WhenA th'e work. has a. thread' provided with asteep face, as for example, a buttress thread where one face of thethread formis-SOF or nearly 90' to the work axis, the tolerance with.respect to this angle is extremely small, and' it isextremely diicult tomachine a, conventional form ofanvil to this form. Such a conventional.form for.' outsidegauging would. be a segment of an internally'threadedpiece which. consequently has a concave periphery for engagement withthe con-` Vex` periphery of, the work piece.. It. is impracti'cabl'e to;grind the steep face of the thread. form in an internally threaded holeto the close tolerances required for gauging.

In accordancewith this invention, therefore, adilerent type. of' anvilis` employed, this being provided with externally formed gaugingelements. Thread rolls might be. employed for such.

necessity makes this. type ofv anvil undesirable,

and to avoid this, instead of helically threaded rolls, in accordancewith this invention. annularly grooves rolls are employed and they arespaced axially ofV the` work, each one to its succeeding one byan amountequal to the lead of the thread between the pointsof contact of. theseveral rolls determined by their angular spacingV about the work.. Theuse of annular grooved rolls, however, maygive rise to a. region ofinterference with the steep faces of the threads of the work because of'th'e factA that the annularly grooved roll has no. lead; Ifsuch a rollis tilted to the. helix angle, this interference will be eliminated, buta. full contact throughout the length of thev roll. will not be obtainedsince the axes of the workpiece and' roll do not thenI lie in acommonplane. In order'to obtain such a full' length contact, in ac.- cordancewithl thisv invention, a conical roll. is

used, the conical roll being tilted toward the axist of the work so asto bring its small endinto vgauging position in linewith the larger end.

parallel to aline through successive corresponding points in the threadperiphery lengthwise. of the work. This tilting` of the conical rollcauses th'e axesof. the roll and the work piece to lie in substantiallyacommon plane in which these axes are not parallel. Substantially where.this. plane intersectsthe peripheries ofthe work piece and theroll;,thesteep: faces of' the roll engage the steep faces' of' properly formedwork threads throughout the axial length common toboth pieceand roll.The tilting of the gauge roll'y axis causes its steep gauging faces,which are. per.-

pendicular to its axis, to be inclined to planesv perpendicular to theaxis of the work, and as these gauge faces recede in opposite directionsaway from the common plane of the two axes; they also separate from theperpendicular work faces. Due to the lead of the threads, the steepfaces of the work also are inclinedto planes perpendicular to the workaxis, this inclination being inamount the lead angle of th'e threads.and on one side ofthe common plane of rtheaxes, this inclination is inthe same direction as the inclination ofthe conicalgauge roll steepfaces. If this inclination of the gauge faces. is slightly greater thanthat of the work faces, which Vis insured by making the roll taperslightly more than the helix angle, the permissible minimum cientlymorethan the helix angle of the thread, as hereinbefore specified.,interference on the steep face of the thread and rolls is eliminated,and.

this taper may be larger th'an this` limit so long as itis notsufliciently great to cause interference on the inclined faces of thethreads. A slight excess of the taper ofl the rol1f over the lead angleis necessary to insure that contact between the gauging 'anvils andAsteep thread faces4 occurs in the plane containingjthe axes of the workpiece and anvil, this excess providing. for clearance elsewhere and toallow fory inaccuracies in that planev to.` elect the gauging action toat least. slightly outside ofthe tolerance limits desired for the gaugeindication. As the inclined facesA cf. the

threads and gauging ridges recede rapidly from each other from thepointsoi maximumcontact,A no interference on these facesv is to beexpected,

provided. these inclined' faces are not. too steep, and th'e angle oftaper and tilt doesnot. greatly exceed the lead angle ofthe threads. Inall cases the direction of taper, that is toward the smaller diameterend; of the. gauging anvilsV is inthe. di-

rection from. the inclined towardithe steep facesof each thread valley.For this reason a single For a more complete understanding of this in#and a washer 28 is placed between its upper end and the head 29 of thescrew. The inclination of the axis of each of the anvils toward the axisof the work piece is such as to bring into parallelism the adjacentgenerating elements of the two surfaces of revolution generally definedby the roll and by the threaded surface of the work, the extent ofangularity of the mounting being equal to that of the taper when gaugingstraight th'reads or equal to the sum or difference of the tapers forVthe roll and tapered threads when gauging tavention, reference may behad to the accompany y ing drawings, in which Figure 1 is a top planView, partly broken away Figure 2 is a sectional view on line 2-2 ofFigure 1.

Figure 3 is a view somewhat similar to a portion'of Figure 2 to a.larger scale and showing one of the gauging anvils in central section.Figure 4 is a fragmentary perspective view showing a modifiedconstruction of gauging anvil.

Figure 5 is a fragmentary view to a larger scale showing the anvil inelevation andthe work in section. Y

, Figure 6 is a detail sectional view on line 6-6 ofFigure5. Y Y

Figures 7 and 8 are side and end elevations, respectively, of a snapgauge for buttress threads.

Figure 9 is a view similar to a portion of Figure l, but showing a gaugefor use with squareor substantially square threads. i

,Figures 10, l1 and Vl2 are detail sectional views on thecorrespondingly numbered section vlines of Figure 9, Figures 1l and 12being drawn to a larger scale. I Y

Referring to the drawings, a work piece provided with buttress threadsis sh'own at I, this being illustrated as engaged with a tubular holder2 supportedona platform 3, this platform having a depending portion 4supported fromthe bed 5 as by spring elements E, the upper ends of whichare outwardly turned` and engaged in slots .in stationary members'IWhich form a part of the bedr 5. .These springs 6 permit some lateralmotionj of th'eiwork to bring it into or out of contact with a pair offixed gauging anvils I0 carried by the bedS.v This support also permitsa sufficient vertical adjustment of the work so that its threads may bebrought intov proper relation to the gauging Yelements of theanvils. Amovable gaugingV anvil II is shown as supported on an arm I2 plv-- otedas by pairs of cross springs I3 and I4 on a stationary supporting postI5. The movable an-v vil ,II may be pressed toward the fixed anvils asby a spring I6 reacting between an arm I 'I secured to the arm I2 and afixed abutment I8, and the position of the gauging element when ingauging position may be shown by a position indicator at having a stem2I against which the arm I2 contacts, the position indicator 20 beingsupported in ,fixed position by the bed 5, as shown in Figure 2. Thisgeneral arrangement of xed and movable anvils withfthe indicatorcontrolled by the position of the movable lanvil is not my invention,which is concerned with the gauging elements per se and their relationto each other.

It will` be noted that each of the gauging elements as shown in Figures1, 2 and 3, is a tapered roll i which'is held on a central support as byascrew 26, the upper end of which is inclined toward the central axis ofthe work. As shownV the gauging anvil 25 isprovided with a centralbushing 21 through which the screw 26 extends pered threads, and inorder that there shall be no interference between the steep faces 3l ofthe work'an'd the corresponding steep faces 32 of the anvil', this'angle must be at least as much as the helix angle of the work threadsbeing gauged. The engagement between the steep thread faces of the workand the corresponding faces of the anvil is shown best in Figure 6. Thelines e-e represent the steep thread faces, being at angles 0,representing the `lead angles, to the lines f-. perpendicular to thework axis fte-h. The curved lines g-g show the apices of the iiatgauging faces of thegauging anvil ribs which are shown as ellipticallines since theyare arcs of circles viewed nearly edgewise at the `angleof tilt, but they are nonsymmetrical with relation to the thread facese-e since, as these gauging faces are peripheral ribs instead ofthreads, they have 84 for gauging work threads of 90.

no lead. The smaller the amount of tiltof the anvils is made,approaching the lead angle, the atter these curves become, approachingthe lines f-f, but anything less than the lead angle brings the linesg-g below the lines e-eto the left of the axis h-h, representinginterference between the anvils and the work which, of course, wouldrender the gauge inoperative for correct gauging. It will be noted thatif the steep face of the work thread is to the work axis, this tiltingof the anvils causes the steep faces of the anvilsto be less than 90 bythe amount Yof tilt. Thus assuming that the angle of tilt a is 6, theangle of the steep faces of the gauging elements will be This `de creaseof the 'angle of the steep thread faces for the anvils which isillustrated clearly in FigureV 5 makesit possible to grind these steepfaces'. accurately; If the steep faces of the work are at less than a 90angle, all the more decrease'i angle is'provided for the anvil steepfaces.

It will be noted from an inspection of Figure 2, that the two anvilsthere shown are spacedaxially by an amount equal to the lead of Ythethread between. the gauging points of contact. Thus the right vhandfixed anvil shown in Figure 2 is shown as mounted somewhat lower thanthe movable anvil Il. The third anvil is similarly axially oifset fromthe others in accordance with the lead between these points of contact.i

In Figure a modifcation'is shown in which instead of employing acomplete conical gauging anvil, the anvil comprises a segment slightlyless than one-third of the complete circumference. This permits one rollto be cut into three segments, each of which may be used where threeanvils are to be employed for gauging a single piece as will usually beprovided.

In Figures 7 and 8 the invention is shown as embodied in a snap gauge,the gauging anvils 50,

being formed and spaced to pass work within the maximum tolerancelimits,and the anvils 5I being formed and spaoedto pass work just belowminimumtolerance limits, the anvils 5I) thus being` go Vanvils and `the anvils5II being not go anvils. l

It will be noted that a set of anvils for gauging work having steepfaces on one side cannot at the same time gauge steep faces on theopposite sides of the threads. Thus, if it be desired to gauge square ornearly square threads, anvils shaped to gauge one steep face and withclearance for the other steep face may be used, and provided the threadst-o be gauged are symmetrical, the work may be subjected to two gaugingoperations with the work facing in opposite directions. Square or'nearlysquare threads may be gauged in a single operation, however, byemploying two sets of oppositely facing anvils, one set for each steepface, in which case opposite thread faces need not be symmetrical if theanvils are shaped to the particular faces to be gauged thereby.

A gauge for gauging square or nearly square threads in a singleoperation with two sets of anvils is shown in Figures 9 to 12,inclusive. Referring to these iigures, two sets of stationary anvils 6Dand 'Bl are employed and one set of movable anvils B2 and 63. Each ofthe sets of anvils is carried by one end portion of a lever r64 or `(i5fulcrumed centrally at 66 and 61, respectively. The two anvils of eachset are reversely disposed, that is, one of the anvils yBIJ is mountedwith its small end upward as shown at the left hand in Figure 10 and itsaxis is inclined upwardly and inwardly, while the other anvil 6| at theright as shown in Figure 10, is arranged with its larger end upwardlyand its axis inclined upwardly and outwardly. The anvils 60 engage theupper steep faces of the square threads 19 of the work as shown inFigure 1l, while the anvils ylil engage on the lower faces of thesethreads 1! as shown in Figure l2, the gauging ribs of each of theseanvils being cut away on the side opposite to the steep gauging faces toclear the oppositely disposed steep faces of the threads. The anvils ofeach set are offset axially of the Work in accordance with the leadadvance between them determined by their angular relationship as in thecase of the gauge provided with the single set of anvils shown inFigures 1 to 4 and 8. Since these two sets of anvils are pivoted forfree equalizing motion from and toward the worky and the anvils forgauging each side of the work thread are symmetrically disposed, theanvils cooperate with each other to produce a true gauging action. Theperipheral edges of the gauging ribs of the anvils may be formed toengage the Work at the roots of the threads, and the side faces of theanvils between the gauging ribs may be formed to engage the outer facesof the threads, so that between the two sets of anvils gauging ofsubstantially the entire thread faces is produced; The anvils 62 and 'B3are mounted on the eoualizins lever 65 carried by the movable arm I2 ofthe gauge in place of the single gauging element shown in Figures 1 and2, and the gauging action may be produced similarly as by means of aposition indicator as shown in Figures 1 and 2.

While as shown the anvils are arranged-for gauging external straightwork, similar anvils may be used for gauging internal work or taperthreaded Work, if desired. In gauging internal work, the curvature ofthe work and of the anvils is in the same direction, so the anvilsshould be of as small diameter as is practicable in order that they maybe given sufficient motion for free gauging action without interference.In gauging taper threads the inclination of the anvil axes will bemodied to suit the taper of the work so as to bring the gauging portionsof each anvil from end to end into the same relation to standard workthreads.

It also will be evident from the foregoing description of certainembodiments of the invention that other changes and modifications mightbe made without departing from the spirit or scope of this invention asdefined by the appended claims.

I claim:

i. A gauge for threads having at least one steep face, said gaugeincluding a plurality of relatively movable gauging anvils, each of saidanvils including at least a portion of an annularly grooved roll taperedat an angle greater than the lead angle of the threads to be gauged,each of said grooves having one face for engagement with the steep faceof the threads and said anvils being offset axially of the Work relativeto each other by amounts equal to the thread lead for the angulardistance by which said anvils are spaced about the axis of the work,said roll portions being tilted to bring the line of gauging actionparallel to a line through successively corresponding points of thethread peripheries lengthwise of the work substantially in a planecontaining the axes of the threaded work and of the tapered roll.

2. A gauge for threads having at least one steep face, said gaugeincluing a plurality of relatively movable gauging anvils, each of saidanvils including a fixed peripheral segmental portion of an annularlygrooved roll tapered at an angle greater than the lead angle of thethreads to be gauged, each of said grooves having one face forengagement with a steep face of the threads and said anvils being offsetaxially of the work relative to each other by amounts equal to thethread lead for the angular distances by which said anvils are spacedabout the aXis of the work, the axes of said roll portions being tiltedto the work axis at the taper angle to bring the line of gauging actionparallel 'to the thread peripheries lengthwise of the work substantiallyin a plane containing the axes of the threaded work and of the taperedroll.

3. A gauge for threads having opposed steep thread faces, said gaugeincluding a pair of sets of relatively movable gauging anvils, each ofsaid anvils including at least an arcuate portion of an annularlygrooved roll tapered at an angle greater than the lead of the threads,the anvils of the two sets being disposed with their smaller diameterends facing in opposite directions and inclined toward the work toengage correctly shaped work threads equally from end to end of thegauging portions of said anvils, each of said anvils having one wall ofeach groove shaped to engage oneside wall of a work thread and theopposite wall free from engagement with the opposite wall of the workthread valley, anvils of the two sets engaging opposite steep faces ofthe work threads and positioned alternately about a central axis inpairs including an anvil of each set, and a pivoted lever to which theanvils of each pair are secured permitting said anvils of the two setsto automatically adjust themselves to the threads of the work when saidanvils are moved relatively into gauging relation to such work, theanvils of each set being offset axially of the work relative to eachother by amounts equal to the thread lead for the angular distances bywhich said anvils are spaced about the axis of the work.

' RAYMOND T. FENN.

